Transportation of bulk materials in the United States is regulated by the United States Department of Transportation, particularly for transportation of hazardous or radioactive materials. See 49 CFR pt. 173 (incorporated by reference). In particular, containers for transportation of hazardous and radioactive materials are required to meet certain design safety criteria. See generally, 49 CFR 173 subpart I. Certain packaging design guidelines for Industrial Packaging, Types 1, 2, or 3, or Type A package (see 40 CFR 173.403) are specified in 49 CFR 410-411. Transportation of bulk materials is similarly regulated in Europe and elsewhere. Bags designed to large scale storage and transportation are typically adapted to carry loads in excess of 10000 pounds.
The United States guidelines specify testing requirements that packaging must undergo to be certified as meeting the guidelines. See 49 CFR 173.465. Included in the testing procedures are a free drop test, and a stacking test. The free drop test requires a package to be loaded or filled to its design weight capacity and dropped from a specific height (1-4 feet, depending on design weight) and to maintain structural integrity after impact. The stack test requires a loaded package to be subject to a compressive load of five times the actual capacity weight of the package. Such testing requirements place substantial restrictions on possible construction of the packaging. For packaging that comprises a flexible bag capable of being lifted when loaded, the drop test and stack test present heavy design hurdles. One possible flexible bag design is shown in U.S. Pat. No. 6,142,727 (the '727 patent), attached hereto and made a part hereof, in its entirety.
The lifting bag in the '727 patent has several drawbacks. First, the lifting straps are attached to the outer cover of the bag, which places stress on the outer cover during lifting operations. Second, the lifting straps encircle the bottom of the bag in an even rectangular grid, which results in an even distribution of weight during lifting provided the lifting forces are evenly distributed. If the lifting forces are not evenly distributed, the bag is subject to torsional forces and the rectangular webbing support grid on the bottom of the bag will not sufficiently compensate for these twisting forces, resulting in bag deformation and unnecessary stress, particularly on the bag seams. Further, an uneven load distribution within the bag can result in torsional forces despite the application of evenly applied lifting forces. Finally, the bag employs a complex flap folding procedure to seal the bag, which is cumbersome and time consuming.
Another lifting bag design is that disclosed in PCT/US06/06662 (the '662 application, hereby incorporated by reference in its entirety). This design uses a bottom support and side support lifting apparatus, where the support members are generally webbing or ropes, and is attached to the bag at designated locations, either on the bottom or the sides, but not the bag top portion. The bag can be constructed from a series of panels. While the bag design is less complicated that that of the '727 patent, construction can be arduous and time consuming.